(i) Field of the Invention
The present invention relates to a transparent resin which has high surface hardness and exhibits excellent scratch resistance, heat resistance and chemical resistance. The invention also relates to a glazing material, a protective cover for display devices, an optical lens and a hard coat material comprising the resin; and a novel polymerizable monomer useful as a raw material for the high surface hardness transparent resin.
(ii) Description of the Prior Art
Methacrylic resin, polycarbonate resin and polystyrene resin exhibit excellent transparency, impact resistance, workability and mass productivity, and therefore have been used as glazing material such as for windowpanes in vehicles, houses, schools and sports facilities, baseboards of verandas, and balconies, protective covers for display devices such as various dashboards, displays for computers, liquid crystal televisions and front boards of vending machines, optical lenses, illuminator covers, signboards, protective glasses, optical photodisc substrates and the like. Particularly, when the above-mentioned resins are applied as glazing materials, protective covers for display devices and as optical lenses, it is necessary that such resins have high scratch resistance, i.e., high surface hardness, chemical resistance, heat resistance and the like to achieve good visibility and desired appearance, transparency, optical physical properties, mechanical strength, stiffness, and the like.
However, the above-mentioned transparent resins are linear polymers, and therefore do not exhibit the requisite surface hardness, chemical resistance and heat resistance. In addition, even if these resins are coated with a hard coat to improve their surface hardness and chemical resistance, sufficient performance cannot always be obtained.
For the purpose of solving these problems, a transparent resin has been proposed which comprises a polymer having a crosslinking structure such as diethylene glycol diallylcarbonate resin or an urethane polyacrylate (Japanese Patent Laid-open Publication Nos. 3610/1986 and 75022/1988).
However, the proposed resins are prepared by the mutual polymerization of an allyl group, an acrylic group or a methacrylic group, polymerization rates of which are on a similar level, and therefore problems exist such as difficulty in controlling the rate of polymerization, run-away reactions, and a long period of time is required to obtain a polymer having a good surface state and a low polymerization strain.